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Dedekind cuts (which are necessary for epsilon-delta proofs) or alternatively Bolzano Weierstrass theorem (if you use sequential convergence definition) imply m
by dnautics 5y ago
Dedekind cuts (which are necessary for epsilon-delta proofs) or alternatively Bolzano Weierstrass theorem (if you use sequential convergence definition) imply multiple sizes of infinity, so the logical arrow is in the other direction, roughly: "real analysis implies assigning different sizes to sets", not "assigning different sizes to sets implies real analysis".
It's been a while but iirc there are other constructions (such as p-adic numbers) which create multiple sizes of infinities out of the rationals which aren't real analysis.
- SAI_Peregrinus 5y agoThe Surreal Numbers are a particularly intuitive sort that create different sizes of infinities. All the ordinals, really. They're isomorphic (in NBG) to a maximal-class hyperreal field of nonstandard analysis.